Punch strippers employing a rubber-like material are well known in the art. These strippers resiliently deflect upon compression but resume their original shape after the compression has been released due to their resilient nature. When they resume their original shape, they will strip the punched workpiece from the punch. U.S. Pat. No. 2,230,043 issued Jan. 28, 1941, shows an early design of such a stripper wherein a rubber spool is disposed about a punch. The rubber spool has bearing plates at each end of the stripper so that it may be applied to the punch either end up. The bearing plates are designed to fit the surface of the sheet metal work. U.S. Pat. No. 2,807,323 also disclothes a resiliently deformable stripper wherein the stripper includes two parts in FIG. 1, the harder part being disposed adjacent the workpiece. In FIG. 5 of this patent, the stripper is formed of dense and soft washers, the softer washer being disposed at either end of the stack. U.S. Pat. No. 3,234,835 discloses that the stripper may be made of a urethane material. U.S. Pat. No. 3,690,205 discloses a two part stripper having a relatively soft urethane tubular portion and a harder nylon portion which contacts the workpiece. Other relevant U.S. Pat. Nos. are 3,211,035, 3,269,238, 3,485,122, 3,871,254, 4,215,608, and 4,428,262.
One problem with urethane strippers which has existed over the years is that while they are relatively durable, they will tear if cut. Thus, all sharp edges of dies and retainers which might come into contact with the urethane stripper must be eliminated to prevent cutting or tearing of the urethane when under load. In recently developed punch assemblies, the surface area of the retainer to be contacted by the stripper is frequently quite small, causing the relatively soft urethane of conventional strippers to extend beyond the surface area of the retainer contacted by the stripper. This will frequently cause tearing or other damage to the stripper.